This invention relates generally to electronic devices, and more particularly, to moisture indicators for electronic devices.
Many electronic devices are susceptible to damage when exposed to excessive moisture. Large stationary devices such as televisions and desktop computers can typically be located in an area of a user's home or office where the likelihood of exposure to liquids can be reduced. For example, a television can be located in a safe environment such as a user's living room, rather than in an outdoors location where the television might be exposed to rain.
Safeguarding other electronic devices can be more difficult. For example, handheld electronic devices and other portable electronic devices are, by their very nature, at a greater risk of accidental exposure to moisture. It is not uncommon for users to carry sensitive equipment such as cellular telephones in a pocket when traveling outdoors. If a user receives a telephone call during a rainstorm, the user might use the cellular telephone before seeking shelter from the rain. Devices may also be left in environments in which condensation may lead to moisture infiltration.
Although devices can be made somewhat resistant to damage from small amounts of moisture, it is not feasible to completely waterproof most devices. For example, device ports may create potential locations through which moisture can reach the circuitry of an electronic device. Covering all of the ports in a device to prevent moisture damage might make the device too cumbersome to use. Moisture barrier structures may also add undesirable bulk and may make devices unsightly and expensive.
Because of these practical considerations, electronic devices are generally somewhat resistant to moisture exposure, but are not completely waterproof. Designing a device in this way maximizes user enjoyment and use of the device, but does not eliminate all risk of moisture-related damage.
Users are generally aware of the moisture sensitivity limits of modern electronic devices. For this reason, users take care to avoid submerging electronic devices in liquid. Even a careless user would not expect an electronic device such as a cellular telephone to be undamaged if fully immersed in liquid.
At the same time, manufacturers try to ensure that devices do not fail immediately upon exposure to trivial amounts of moisture. Overly sensitive devices would require frequent attention from customer service personnel.
Even though electronic devices are generally designed to be robust enough to withstand momentary exposure to trivial amounts of moisture, accidents can happen. For example, a user may drop a device into a body of water. When a device that has been damaged in this way stops working properly, the user may decide to return the device to the manufacturer for repair.
A large manufacturer of electronic devices can expect to receive returns from customers that have exposed their devices to excessive amounts of water. Often the damaged devices are dry when they are returned. To determine whether or not a device has been submerged in liquid, manufacturers often include moisture infiltration indicators (sometimes called “water dots” or “moisture indicators”) in their devices. If the water dot in a returned device has not been activated, the manufacturer can conclude that damage to the device was caused by dropping the device onto a hard surface or another damaging event other than liquid exposure. If the water dot has been activated, the manufacturer can conclude that the device has failed due to excessive exposure to liquid.
The use of water dots to test for liquid exposure helps manufacturers to evaluate warranty claims and debug possible failure mechanisms. To avoid adversely affecting device aesthetics, it is often desirable to place water dots in discrete locations. At the same time, it may be desirable to place water dots in locations that are readily accessible by service personnel, so that a returned device does not need to be disassembled to examine the status of the water dot.
As an example, a water dot may be placed in a recessed portion of a device such as a device port. When a water dot is located in a device port, the water dot can be quickly examined by service personnel, but will not be unsightly to users.
Particularly when water dots are located in relatively exposed positions such as these, the water dots may become highly sensitive to moisture damage. This may make it impossible for service personnel to determine whether a device has failed from a small amount of moisture exposure of the type that would normally be covered by the manufacturer's warranty or whether the device has failed due to a complete submersion of the device in liquid.
It would therefore be desirable to be able to provide improved moisture indicator structures for electronic devices.